1. Field of the Invention
This invention relates to locking handles for surgical trocar assemblies and more particularly to automatic locking handles which lock the handles prior to insertion into body tissue and which automatically releases the lock when the trocar assembly is inserted into the body tissue.
2. Description of the Prior Art
In endoscopic surgical procedures, surgery is performed in any hollow viscus of the body through narrow endoscopic tubes (or cannula) inserted through small entrance wounds in the skin. Similarly, in laparoscopic surgical procedures, surgery is performed in the interior of the abdomen through a small incision. In order to perform these procedures, a trocar assembly is utilized to facilitate the insertion of cannulas into the body. Trocars are sharp pointed surgical instruments used to puncture a body cavity which are generally adapted to be used together with the cannula. Once the body cavity has been punctured by the trocar, the trocar is removed from the cannula, thereby leaving the cannula extending into the body cavity. Endoscopic or laparoscopic surgical procedures are then performed through the cannula with accessory instrumentation such as laparoscopes, dissectors, graspers, and the like.
One type of commercially available safety trocar assembly, includes a spring-biased safety shield which is adapted to cover the trocar tip once the body cavity has been entered so as to provide an increased level of protection to internal structures from puncture or laceration. For example, U.S. Pat. No. 4,601,710 to Moll describes one type of trocar assembly which consists of two subassemblies: an obturator (or trocar) subassembly which includes an obturator tip (or sharp-tipped trocar) and a spring-loaded tubular safety shield positioned therearound, and a cannula subassembly. When ready for use, the obturator subassembly is inserted through the cannula subassembly. With the safety shield initially in its distal-most position covering the obturator tip, pressure is exerted against the skin with the trocar assembly causing the shield to be pushed rearwardly against the spring to expose the piercing tip of the trocar assembly. The tip penetrates the skin and underlying tissue with continued pressure. Once the tip has penetrated through the wall and has entered the cavity, the force against the front end of the shield ceases and the shield is automatically moved back to its distally extended position. Viscera and other internal tissue are thus protected from contact with the sharp piercing tip and potential damage therefrom.
U.S. Pat. No. 5,116,353 to Green (commonly assigned) describes another type of safety trocar assembly which includes an obturator subassembly having an automatically retracting obturator tip and a cannula subassembly. In operation, the obturator subassembly is inserted through the cannula subassembly and the sharp tip of the obturator subassembly is extended to its distal-most position. Exertion of pressure against the body wall will cause the sharp tip trocar to penetrate the body wall. Once the sharp tip penetrates the body wall, the counterforce against the sharp tip will cease causing the sharp tip to automatically retract into the cannula subassembly. Viscera and other internal tissue are thus protected from contact with the sharp piercing tip and potential damage therefrom.
When using the safety trocar assembly described in Green Pat. No. 5,116,353, if the surgeon inserts the trocar assembly through the body tissue in a manner that does not maintain the obturator subassembly in close approximation to the cannula subassembly when pressure is applied to the trocar assembly, the obturator subassembly may slide proximally, allowing the sharp tip to move away from the tissue.
Accordingly, it would be desirable to assist the surgeon in such procedures by providing a trocar assembly which automatically locks the obturator subassembly to the cannula subassembly before the surgeon inserts the trocar assembly into the body tissue.